Enhanced anti-oxidant activity of neoagarooligosaccharides produced by β-agarase derived from Aquimarina agarilytica NI125

Abstract

The neoagarooligosaccharides have received growing attention owing to their physiological activities. The aim of this study was the isolation of agarase-producing bacteria for production of agar hydrolysates with special emphasis on their anti-oxidant potential. An agarolytic strain NI125 was isolated from Nelson's Island, Alexandria, Egypt. Based on 16S rRNA analysis and extensive phenotypic characterization, it was identified as Aquimarina agarilytica. Maximum enzyme production was achieved after 24 h incubation at 20°C, and tryptone was recorded to be the best nitrogen source for agarase production. Extracellular agarase was partially purified by ammonium sulfate precipitation. The substrate specificity assay using p-nitrophenyl-α/β-D-galactopyranoside revealed the cleavage of the β-linkage rather than the α-linkage. Neoagarooligosaccharides produced by the partially purified β-agarase expressed promising anti-oxidant properties, with 23% free radical scavenging potential. Notable enhancement of the anti-oxidant potency of the oligosaccharides was achieved (up to 87% scavenging ability) by sulfation of the agar prior to hydrolysis for 12 h with β-agarase. Results obtained suggest the potential application of the produced neoagarooligosaccharides anti-oxidants as promising additives in food and feed products.